The long-term objective of this project is to evaluate the ecological role of bacteriophages in the subgingival region of the oral cavity. The immediate objective of this project is to obtain temperate and lytic phages for selected strains of gram-negative anaerobic bacterial species which are found in subgingival plaque and which are believed to be important in periodontal diseases. By using standard lysogen-inducing treatments followed by plating on a newly-developed indicator medium, attempts will be made to identify and isolate cured lysogens, which will then be used as phage indicator strains to isolate the temperate phages which infect them. Standard mutagenesis techniques will also be used to isolate virulent mutants of the temperate phages carried by each strain. The availability of both temperate and virulent phage will allow numerous types of experiments to be carried out, which are not presently possible with periodontal pathogens, such as phage (& prophage) typing of clinical isolates, isolation of bacterial cell surface mutants (as phage-resistant mutants), and attempts to transduce bacterial genes between related genera and species.